Various means have been employed over the years to practice the so-called activated sludge process for treating waste water. One conventional apparatus is a so-called "oxidation ditch" wherein an elongated vessel is provided with a central wall dividing the vessel into two channels connected at their opposed ends. Some sort of means, frequently a rotor, is employed to introduce oxygen into the waste water and move the same through the oxidation ditch in a closed loop path.
Effluent from the ditch is frequently taken to a separate vessel which acts as a clarifier or, in the alternative, may enter a separator within the oxidation ditch, frequently mounted on one of the side walls thereof, from which clarified liquid may be withdrawn.
While these various structures have generally worked quite well for their intended purpose, they are not without cost, particularly where a separate clarification vessel must be constructed. In order to avoid the cost difficulties, the prior art has proposed the use of so-called sequencing batch reactor processes to accomplish the same thing. In these reactors, a single vessel is first used for aeration. After attaining the desired degree of aeration, the aeration process is halted and clarification is allowed to occur with withdrawal of the clarified effluent. Once withdrawal of the clarified effluent has been accomplished to the desired degree, the aeration process may be reinstituted.
Again, while this type of structure and process work well for their intended purpose, batch operation is not desirable, or even tolerable in every instance since influent flow, though variable, is generally continuous.
The present invention is directed to overcoming one or more of the above problems.